Now, ebooks are not only being publicized as a method of producing a passive income stream, there's a second tier of revenue being created with the ability to insert advertisements into your ebooks. You know, like print magazines now.
For more information, like how you give potential advertisers concrete numbers when you don't have subscription counts like the magazines they're used to dealing with in budgeting ad expense, check out Stu McLaren's article and Eldon Sarte's suggestionsover at Wordpreneur.